This invention relates in general to multicylinder internal combustion engines for motor vehicles in which at least one group of cylinders is rendered inactive in response to at least one operational parameter of the engine.
From the German publication DE-OS No. 2,942,851 a device for disconnecting at least one cylinder in a multi-cylinder internal combustion engine in dependence on at least one operational parameter is known. In this prior-art device an electrical regulator is provided for controlling rate speed of the vehicle, so that after the connection or disconnection of the cylinders a corrective motion of throttle valves is performed. By means of this measure a power jump during the cylinder changeover is to be compensated for. A similar device is known from the German published patent application DE-AS No. 2,947,688, in which also the throttling valve acting as the regulating member executes a sudden or jerky movement during the cylinder changeover. The magnitude of this jump of the throttle valve is made dependent on the rotary speed of the machine, in such a manner that the load and torque of the machine during the connection or disconnection of the cylinders remains unchanged.
The sudden angular change of the position of the throttle for the purpose of preserving the power of the internal combustion engine during the connection or disconnection of the cylinders is known also from the German publication DE-OS No. 2,612,172.
The latter publication employs for this purpose a special linkage; on the other hand, the aforementioned two publications disclose electronic control devices.
One of the disadvantages of the prior-art devices is a one-sided wear of a certain cylinder or cylinder groups; another disadvantage of prior-art solutions is the necessity of warming up the cylinder or cylinder groups after their switchover.
Individual problems have been also approached in the German publications DE-OS Nos. 2,724,487 and 3,023,180. In the prior-art multi-cylinder internal combustion engine according to the publication No. 2,724,487, there is provided a device having a variable threshold value which is derived from the rotary speed of the engine and made dependent on the engine load. When the load during the run of the engine drops below or rises above the variable threshold value, the fuel supply for a part of the cylinders is interrupted or changed over. In the internal combustion engine known from the German publication No. 3,023,180, starting performance and warm running quality of the engine is improved in such a manner that the warm running is always performed with the full number of cylinders. However, when the engine is warmed up, then during its unloaded operation a part of the cylinder is disconnected. However, even these two last mentioned publications do not solve the problem of the one-sided wear of some of the cylinders and do not consider the cooling down of the unused cylinders. Similarly, in the engine according to the publication No. 3,023,180, the full number of the cylinders is switched over when the total temperature of the engine drops below a certain value.